import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

public class CityFreqRankMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
    private final static IntWritable v = new IntWritable(1);


    @Override

    protected void map(LongWritable key, Text value, Context context)

            throws IOException, InterruptedException {//整个过程去重
//按tab分割
        String line = value.toString();
        String[] fields = line.split("\t");
        Text keyOut = new Text(fields[3]);
        //map输出key，value
        context.write(keyOut,v);
    }

}
